This grant application seeks support to develop preliminary data concerning a behavioral intervention aimed at ameliorating age-associated cognitive decline. It will investigate the effect of an aerobic fitness intervention on cognitive function in elderly individuals with Mild Cognitive Impairment (MCI). MCI has been recognized as a transitional condition in the development of Alzheimer's Disease (AD). Recent studies have shown that aerobic exercise potentiates neurogenesis in the hippocampus and neocortex and enhances cognitive abilities mediated by these brain structures in elderly adults. Exercise also has been shown to increase neurotrophic factors. Furthermore, inverse relationships have been observed in the aged between glucocorticoid levels and hippocampal and neocortical integrity, and elevations of cortisol have been implicated in AD. We propose an exploratory study evaluating the efficacy of an aerobic exercise intervention in enhancing cognitive function in MCI. A secondary goal is assessment of the effect of the intervention on modulation of basal cortisol level, an indirect index of hippocampal and neocortical integrity. In a randomized, controlled study, we will conduct a 12-week aerobic conditioning program with previously sedentary men and women with Mild Cognitive Impairment. We will investigate changes in executive function ability, episodic memory function, and basal cortisol. Changes in mood, cardiac function, and aerobic capacity also will be assessed as possible mediating factors. The findings of this study would represent an initial but essential step in evaluating the efficacy of aerobic exercise as a behavioral factor that ultimately might be found to delay, arrest, or conceivably reverse progression of age-related cognitive decline. It also would yield data indicating the effectiveness of the intervention in modulating cortisol, elevation of which is associated with substantial risk for cerebral deterioration in the elderly. The demonstration of an ameliorating effect would provide the basis for future investigations examining the specific nature of the cognitive-cerebral adaptations to exercise, the relative benefits of different forms of exercise, and issues of dosage and duration of effect. [unreadable] [unreadable]